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 By giving" &" at end of script called running background                             (OR) Set in task scheduler or crontjob . Using at command you can schedule a job to run at a particular date and time. For example, to execute the backup script at 5 a.m tomorrow, do the following. $ at -f backup.sh 5 am tomorrow you can run the shell script Following methods at backgroundly : . script.sh & ./script.sh & sh script.sh &        (OR) nohub sh script.sh & nohub ./script.sh & nohub . s cript.sh & Note: hup  is a hangup signal... nohup - no hangup... so if we give  nohup script.sh & ... it starts progressing script.sh in back ground... that the subsequent logout or session disconnection does not stop.. Note:  & Stands for running background After running this give  "ctrl+z" in background one id will be displayed a...

Crontab file consists of command per line and have six fields actually and separated either of space or tab. The beginning five fields represent time to run tasks and last field is for command. Minute (hold values between 0-59) Hour (hold values between 0-23) Day of Month (hold values between 1-31) Month of the year (hold values between 1-12 or Jan-Dec, you can use first three letters of each month’s name i.e Jan or Jun.) Day of week (hold values between 0-6 or Sun-Sat, Here also you can use first three letters of each day’s name i.e Sun or Wed. )  +---------- minute (0 - 59)  ¦ +-------- hour (0 - 23)  ¦ ¦ +------ day of month (1 - 31)  ¦ ¦ ¦ +---- month (1 - 12)  ¦ ¦ ¦ ¦ +-- day of week (0 - 6 => Sunday - Saturday, or  ¦ ¦ ¦ ¦ ¦                1 - 7 => Monday - Sunday)  ? ? ? ? ?  * * * * * command to be executed  0 -> Sun  1 -> Mon  2 -> Tue ...

In this article we are going to review and see how we can schedule and run tasks in the background automatically at regular intervals using  Crontab  command. Dealing a frequent job manually is a daunting task for system administrator. Such process can be schedule and run automatically in the background without human intervene using cron daemon in Linux or Unix-like operating system. For instance, you can automate process like  backup ,  schedule updates  and  synchronization of files  and many more.  Cron  is a daemon to run schedule tasks. Cron wakes up every minute and checks schedule tasks in crontable.  Crontab  ( CRON TABle ) is a table where we can schedule such kind of repeated tasks. Tips:  Each user can have their own crontab to create, modify and delete tasks. By default  cron  is enable to users, however we can restrict adding entry in  /etc/cron.deny  file. Crontab file consists of comma...